Serial port pinouts

VEX Controller:

Pin1: TTL-CTS (the right most pin when looking at the front of the connector on the Vex Controller)
Pin2: + 5V out (1 Amp max from all external +5 V pins combined)
Pin3: TTL-RTS
Pin4: Ground
Pin5: TTL-RX in
Pin6: TTL-TX out (the left most pin when looking at the front of the connector on the Vex Controller)

TS-7260 COM3

NC RTS CTS NC NC
NC RXD TXD NC GND

With OP2-TTLCOM, COM3 lines become TTL and only RXD and TXD are used, and lines are available on the XDIO lines.

To connect these, a cable (RJ12 on VEX to 16 pin socket connector of some kind on TS-7260) will be needed.

http://xtronics.com/reference/10baseT.htm for info on RJ12